Question

Draw the structures of major monohalogenation products in the following reactions:

Hint:

Free radical halogenation under UV/light occurs preferentially at benzylic positions due to resonance stabilization.

Answer 1

(a) The reaction is a free radical halogenation at the benzylic position: \[ \text{NO}_2–C_6H_4–CH_2CH_3 \xrightarrow{\text{Br}_2, h\nu} \text{NO}_2–C_6H_4–CHBrCH_3 \] (b) Toluene undergoes benzylic chlorination: \[ \text{C}_6\text{H}_5–CH_3 \xrightarrow{\text{Cl}_2, h\nu} \text{C}_6\text{H}_5–CH_2Cl \] Only one hydrogen is replaced at the benzylic position in monohalogenation.